The present invention relates to an apparatus for filling containers, and, more particularly, to a fill pump having an improved configuration for attaching a diaphragm seal therein.
Packaging machines are known that integrate the various components necessary to fill and seal a container into a single machine unit. This packaging process, generally stated, includes feeding carton blanks into the machine, sealing the bottom of the cartons, filling the cartons with the desired contents, sealing the tops of the cartons, and then off-loading the filled cartons for shipping.
Trends within the field of packaging machines point toward increasingly high capacity machines capable of rapid, continuous filling and sealing of a very large number of identical or similar packaging containers, e.g., containers of the type intended for liquid contents such as milk, juice, and the like. One such machine is disclosed in U.S. Pat. No. 5,488,812, issued Feb. 6, 1996, and entitled "A Packaging Machine." The machine disclosed in that patent includes a plurality of processing stations, each station implementing one or more processes to form, fill, and seal the containers. Each of the processing stations is driven by one or more servomotors that drive the various components of each of the processing stations. Other packaging machine types include machines sold by Tetra Pak, Inc., under the TR/6.TM., TR/7.TM., and TR/8.TM. trademarks.
The increased throughput and decreased size requirements that packagers have placed on their packaging machines have increased the demands that are placed on the fill systems that are employed. Various apparatus and corresponding methods for filling containers, such as gable-top containers, have therefor been devised for these machines. In accordance with one of the more popular filling methods, the container is lifted from a conveyor to a fill pipe by means of a lifting mechanism. The container lifting mechanism gradually lowers the container as product is dispensed through the fill pipe. The container is lowered until it again engages the conveyor where it is transported to a subsequent processing station, such as a top sealing station. Such a method is utilized in the packaging machines referenced above.
Alternatively, the filling and top sealing operations may be performed at a single location within the machine. In such instances, the container may be top sealed at the filling station after it has been lowered from the fill pipe. Such a method and apparatus are shown and described in the referenced '812 patent.
Many of the foregoing systems utilize a diaphragm for isolating the moving components of the pump mechanism of the fill system from the flow of product. The diaphragm is attached to the head of a piston using, for example, an adhesive bond. During operation of such a system, the piston is driven so that it moves the diaphragm to alternatingly decrease and increase the volume of a pump chamber to expel and suction fluid, respectively. Such repetitive movement creates stress on the adhesive bond attaching the diaphragm to the head of the piston. Over time, the adhesive bond could be subject to failure, and the diaphragm would then be either repaired or replaced. Such failures increase the cost of running the machine and result in costly down time during which the machine is not packaging product. The inventors of the present invention have recognized a need for a fill pump having a diaphragm that secures the diaphragm to its drive while overcoming the problems associated with the current attachment methods.
Another problem encountered with certain pump mechanisms relates to the dosing of the product. More particularly, many systems experience inaccuracies when attempting to dispense uniform volumes of product in a precise and repeatable manner during a high carton throughput filling operation. The inventors of this application have recognized a need for an apparatus that delivers reproducible, precise amounts of product in a high volume filling system.